In the field of ordinary structural concretes, in particular concretes of the C25/30 type (that is to say, for which the typical compressive strength 28 days after mixing, measured on a 16×32 cm cylinder is at least 25 MPa, and measured on a 15×15 cm cube is at least 30 MPa according to the EN 206-1 Standard), or in the case of the C20/25 type of concretes (whose characteristic compressive strength 28 days after mixing, measured on a 16×32 cm cylinder is at least 20 MPa, and measured on a 15×15 cm cube is at least 25 MPa according to the EN 206-1 Standard) it has been noted that the quantity of cement is typically from 260 to 360 kg per m3 of concrete. Current European standards moreover do not provide levels of cement less than 260 kg/m3 for ordinary structural concretes.
Now, the processes for cement production, and more particularly its essential constituent, clinker, are responsible for high emissions of carbon dioxide. The production of grains of clinker in fact requires:                a) pre-heating and decarbonation of the raw meal which is obtained by grinding the raw materials, which are, in particular, limestone and clay; and        b) firing or clinkering the meal at a temperature of 1450-1550° C., followed by rapid cooling.        
These two stages produce CO2, on the one hand as a direct product of the decarbonation and on the other hand as a by-product of the combustion which is implemented in the firing stage in order to raise the temperature.
The emission level reaches approximately 560 kg of CO2 per tonne of binder for a binder typically used to produce a C25/30 concrete, which contains 65% of clinker (on the basis of an average emission of 850 kg of CO2 per tonne of clinker).
Now, the high emissions of carbon dioxide in standard processes for the production of cement and concrete compositions constitute a major environmental problem, and, in the current context, are subject to high economic penalties.
A strong need therefore exists for a process capable of producing concrete with reduced associated emissions of carbon dioxide, the said concrete providing satisfactory mechanical properties, and in particular a C20/25 or C25/30 type of concrete.
Advantageously, the concrete according to the invention has an arithmetic average of compressive strengths greater than or equal to 6 MPa, preferably greater than or equal to 7 MPa, at 20° C. 24 hours after mixing, the measurement being carried out according to the EN 12390-3 Standard on cylindrical specimens, kept according to the EN 12390-2 Standard at 20° C.±2° C. and relative humidity greater than 95%.
Advantageously the rheological properties of the wet concrete are satisfactory and provide good workability, which is to say that the consistency of the mixed batch is suitable for easy handling, even two hours after mixing.